Aggressive research efforts by Belgian veterinarians have culminated in the identification of numerous indicators or factors--including horse management and pasture characteristics--associated with atypical myopathy, a rapidly developing and fatal disease that destroys skeletal muscles.

"Atypical myopathy is sporadically seen in grazing horses in the United Kingdom and other European countries such as Austria, Belgium, France, Germany, and Switzerland, among others," reported Dominique Votion, DVM, PhD, from the Equine European Centre of Mont-le-Soie and Department of Clinical Sciences at the University of Liège in Belgium.

Typical signs of atypical myopathy include sudden onset of muscle weakness, stiffness, horses that are recumbent and unable to rise, and the production of dark colored urine.

Since atypical myopathy is typically fatal and no treatment or specific disease prevention strategies are currently available, the goal of this study was to identify risk factors for atypical myopathy to potentially identify ways to limit the development of the disease.

In this retrospective study, 57 clinical cases of atypical myopathy diagnosed between November 2000 and May 2005 were included. In addition, information from horses free of atypical myopathy that did (77) or did not (386) graze on the same pasture as the affected horses was also collected.

"Our results indicate that both horse and environmental factors are associated with the development of atypical myopathy," said Votion.

In particular, young, inactive horses in poor or normal body condition (but not overweight horses) might have a higher risk of developing atypical myopathy. Further, permanent pasturing of the horse and spreading of manure as well as humid, sloping pastures with an accumulation of dead leaves could each predispose horses on pasture to the development of atypical myopathy.

According to Votion, instituting interventions based on these identified risk factors might decrease the likelihood of pastured horses developing atypical myopathy.

"More research is needed to determine the cause of atypical myopathy and a focused awareness of this condition is essential," Votion added. "In addition, accurate epidemiological data would be of great help in our quest for the aetiological agents and to strengthen our knowledge base of identified indicators or risk and protective factors."

"Atypical myopathy in grazing horses: A first exploratory data analysis," is scheduled for publication in an upcoming edition of The Veterinary Journal. The abstract is currently available on Pubmed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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